A conventional electromagnetic actuator includes a rotor, a stator, and coils. In such a conventional electromagnetic actuator, the rotor is magnetized with magnetic poles (the N pole and the S pole), and can reciprocate at predetermined angles (or within an operating range). The stator has magnetic poles arranged to face the outer peripheral face of the rotor. The coils for excitation are wound around the stator.
FIG. 10 illustrates the structure of a conventional electromagnetic actuator that is disclosed in Japanese Utility Model Publication No. 4-47697. In the electromagnetic actuator illustrated in FIG. 10, a rotor housing that is formed with an upper plate 100 and a lower plate 101 both made of plastic is disposed so as to house a rotor 102, a stator 103 positioned to face the outer peripheral face of the rotor 102, and a coil 104 that is wound around the stator 103.
At present, such an electromagnetic actuator is expected to be even smaller, as devices to which the electromagnetic actuator is to be mounted have become smaller. Particularly, with respect to electronic devices that have rapidly become smaller and sophisticated, such as cameras and portable telephone devices with camera functions, the electromagnetic actuators to be used in sector devices such as shutter devices and aperture devices are strongly expected to become smaller.
In the above described electromagnetic actuator disclosed in Japanese Utility Model Publication No. 4-47697, however, the rotor housing needs to be large enough to accommodate the rotor 102, the stator 103, and the coil 104. Therefore, there is a limitation on the reduction in electromagnetic actuator size.
Therefore, the object of the present invention is to provide a smaller electromagnetic actuator.